1. Field of the Invention
The present invention relates generally to an effusion cell assembly installed in an epitaxial apparatus, and particularly an effusion cell assembly for epitaxial apparatus capable of easily assembling and disassemblying a cell assembly with entire vacuum maintained in a vacuum chamber.
2. Description of Related Art
Generally, a cell assembly of the epitaxial apparatus, i.e., effusion cell emits effusion vapors by heating raw material in an ultra vacuum chamber, in which a heating coil is wound around the cell and the raw material in the cell is heated and effused by applying current to the heating coil. In such a molecular monocrystal growing apparatus, its quality of the produced product is influenced by an amount of included impurity, and its degree of vacuum in the ultra vacuum apparatus depends on the amount of impurity included in the vacuum chamber. Since the degree of vacuum determines the quality of monocrystal material, i.e., semiconductor material, it is very important to prevent contamination in the, vacuum chamber.
Particularly, the ultra high vacuum apparatus, i.e., molecular epitaxy apparatus have to maintain a state of ultra very vacuum in view of its characteristic, and minimize, in the vacuum chamber, inflow of general atmosphere materials, i.e., air and elements adhered inside the epitaxial apparatus and influenced on the vacuum. When growing atomic unit of monocrystal using the above apparatus, since it necessary to minimize the impurity, its exposed time in the atmosphere must be minimized in any case and its exposal must be prevented, if possible.
Prior art epitaxial apparatus having the effusion cell is now explained with reference to FIG. 1.
As shown in FIG. 1, the effusion cell 10, which material to be grown is filled, is installed at one end of the vacuum chamber 1, and an adaptor 4 for coupling the cell assembly in the vacuum chamber is located between an entrance flange 2 of the vacuum chamber 1 and a cell flange 7. The adaptor 4 has a pair of flanges 3 and 6 at both sides to connect between the entrance flange 2 of the vacuum chamber 1 and the cell flange 7, in which a lead-in duct a for supporting the effusion cell 10 in the vacuum chamber 1 and a liquid nitrogen wall 9 for surrounding the lead-in duct 8 are installed through the adaptor 4 inside the vacuum chamber 1.
In such an epitaxial apparatus, the prior art effusion cell assembly has the effusion cell 10 filled with the growing material, a heater 11 for supplying heats to effuse the growing material, the lead-in duct 8 for supporting the heater 11, and the cell flange 7 for fixing the lead-in duct 8 and coupling the adaptor flange 6 as shown in FIG. 2.
In the above epitaxial apparatus, if the raw material filled in the effusion cell is drained, after disassemblying the respective flanges connected through the adaptor flange and releasing the vacuum, it required that the cell be separated from the vacuum apparatus and be exposed in the atmosphere to charge the raw material.
That is, when the growing material is charged again and the broken call is repaired, though both the cell and the heater are small, all the vacuum in the vacuum apparatus must be released.
Such a vacuum breakdown causes the air to inflow in the vacuum chamber, so that impurities in the air are adhered inside the vacuum chamber and thus, the impurites may be adhered to, for example, semiconductor substrate when, using the vacuum apparatus. The undesired impurites deteriorate the quality of products and use of the produced products is impossible.